Back in the days I had the 1E rules, I got by for a year or so just using the monster summary tables in the DMG before getting the MM. It's not something I'd ever do again, I want pictures with my monsters.
As for presentation, I want the combat block on one page, and one page only - no page flipping, please. If I could, I'd really like a book that has a pocket for each monster with a 5"X7" index card I can pull out when I need to run them at the table, then put it back into the book for when casually reading or planning the next adventure.
Artwork of the creature is vital to me. I can get by without it, but good, evocative art is fun to show off to players and can really inspire ideas for encounters.
The rest of the entry I would like in an Ecology or 2E format, but not overly wordy so mechanics are hidden in a paragraph block and absolutely no bullet points. I don't mind if the whole presentation of a monster ends up taking 3-4 pages, but they don't have to - a half or quarter page for something like a bear would be fine, but maybe an orc gets the full four pages, with several varieties statted up (warrior, warlord, shaman, etc.).
I don't want monster lore to get as deep as Volo's did, as that's a bit too stifling, but giving some basic information how they could fit into a campaign world or encounter ideas would be acceptable ("goblins prefer to set up camps within a perimeter made of brambles or stacked deadwood that is adorned with trophies taken from combats as signs of their prowess. Usually they set up a pen where they keep any Wargs for riding and not far off will be any cages where the goblins hold any prisoners they've taken. If the goblins are on the war trail they may forgo the perimeter wall for some sort of natural barricade or obstacle and prisoners may simply be tied to nearby trees or posts driven into the ground.")
When it comes to spells, I wouldn't be against a curated list in the combat stat block, but I'd also like a sidebar with the full list to use if I needed one to go. A suggested tactics block covering 3-4 rounds would be good for complex creatures or ones that have some sort of "combo" sequence that their CR is based off of.